The solid solutions M0,1Zr0,18Ce0,72O2, where M is a rare earth metal (REM) are synthesized. The structural and textural characteristics of prepared compositions were studied by XRD, Raman spectroscopy, TEM and low-temperature nitrogen adsorption. It is shown that the introduction of 10 mol.% REM in the solid solution Zr0,2Ce0,8O2 allows to save the cubic fluorite structure. In this case the parameter of lattice of solid solution decreases with increasing the atomic number of REM. The synthesized samples are nanosized: the ceria crystallite size is 13,3 nm, Zr0,2Ce0,8O2 – 11,2 nm, M0,1Zr0,18Ce0,72O2 – about 8 nm. According to TEM, the average particle size is 15 nm. The incorporation of REM increases the specific surface area and porosity due to the formation of more defective structure. There is determination of the catalytic activity of the synthesized solid solutions in CO oxidation in a flow reactor under the conditions: pressure 0,1 MPa, temperature of 20–500 °C, space velocity of 1800 h–1 gas mixture (vol.%): CO – 3,6; O2 – 8,0; N2 – balance. The samples with light REM (praseodymium, samarium, neodymium) were the most active, they have a high oxygen storage capacity (OSC). That new catalysts have an interest for the purification processes from gas emissions of motor vehicles.